This invention is directed to an improved transmission having geared steer which avoids the necessity of brake steering. More particularly, this invention is directed to a cross drive planetary transmission for a track-type vehicle which provides a plurality of forward and reverse speeds with alternate power turn radii steering options. Still further, this invention includes a provision for hydraulic disengagement of the transmission brake.
In track-type vehicles as used in the earthmoving industry, transmissions having brakes are frequently employed. Steering is accomplished by application of the brakes with attendant disadvantages. With band-type vehicles, for example, the brakes have limited capacity for a given drum size and require cooling systems and self-adjusting actuating linkages. Because of these and other problems larger vehicles have gone over to disc-type power shift brakes. However, this has not completely eliminated the aforementioned problems.
Another problem is the requirement that the track-type vehicle be capable of performing a variety of dissimilar tasks. For instance, such a vehicle may be called upon to haul heavy loads at relatively high speeds as in the construction industry. At the same time the vehicle must be capable of adapting to operation as a low speed high torque vehicle in a variety of applications such as when in drawbar applications.
Another problem relates to construction of the transmission in relation to the vehicle. To facilitate assembly, servicing and maintenance, it is desirable to construct the transmission arrangement so that it may be easily assembled and removed, preferably as major units or modules.
Still another problem is a result of the transmission brake being normally engaged and hydraulically disengaged. In the absence of vehicle hydraulic pressure, as during vehicle breakdown, the transmission is undesirably engaged, which is detrimental to towing of the vehicle.